Effect of ankle position and a plaster cast on intramuscular pressure in the human leg.

Intramuscular pressure was measured with transducer-tipped catheters that had been inserted into the anterior and deep posterior compartments of the leg in seven healthy adults. Intramuscular pressure increased three to sevenfold (depending on the position of the ankle) in both compartments after the application of a plaster cast from the proximal part of the thigh to the malleoli. While the cast was in place, the baseline intramuscular pressure was elevated by the inflation of a tourniquet, which was located on the proximal part of the thigh, to a pressure of sixty millimeters of mercury (8.00 kilopascals). The intramuscular pressure in both the anterior and the deep posterior compartments was found to be lowest when the ankle joint was between the neutral and the resting positions (between 0 and 37 degrees of flexion). After the cast was bivalved and the opening on each side was spread approximately one-half centimeter, there was a significant decrease in intramuscular pressure of 47 per cent in the anterior compartment and of 33 per cent in the deep posterior compartment (p < 0.05 for both).